Just use the memo.cash protocol and put it on the bitcoin cash blockchain for a fraction of the price (you just pay the BCH transaction fee). You're limited on the message size but the May 15 blockchain upgrade will increase the OP_RETURN limit and put the limit slightly higher than twitter's.

The ability to store arbitrary data on these widely replicated blockchains raises some serious legal questions. What if someone puts illegal information on the blockchain (e.g. nuclear secrets, child porn)?

Even if some level of mens rea is required convictions, that is usually set at "reckless" (meaning that you were aware of the risk but acted anyway). Once there's a high-profile child-porn-on-the-blockchain case, it would be very hard to argue that you weren't at least aware of the risk that such information might be there. Even if the mens rea requirement is "knowing", that will still be a problem, as bitcoin miners and other savvy cryptocurrency actors would have a hard time claiming ignorance of the immutable nature of the blockchain.

> Based on these insights, we conduct a thorough quantitative and qualitative analysis of unintended content on Bitcoin’s blockchain. Although most data originates from benign extensions to Bitcoin’s protocol, our analysis reveals
more than 1600 files on the blockchain, over 99 % of which are texts or images. Among these files there is clearly objectionable content such as links to child pornography, which is distributed to all Bitcoin participants.

There is a cost, but larger pieces of data can be broken into chunks and stored on the blockchain. Some types of data are considered breaking the law to possess it, regardless of whether it was intentional or how it was acquired.

Can data broken up like that can be said to be in your possession if it is never recombined? What if you don't know how to recombine it but a prosecutor does? What if it is known to be recombinable but no one knows how to recombine it?

Most blockchain people I talk to are worryingly dismissive of this as a potential issue, including lawyers.

A while ago, I built a prototype that did something somewhat similar with IPFS instead of blockchain. It also pinned the IPFS object automatically. It saved the entire tweet minus all mutable attributes (user info, retweet count, etc).